Thermal modulation of pyruvate metabolism in the fish Gillichthys mirabilis: The role of lactate dehydrogenases

TLDR: Temperature-dependent kinetic properties may give the LDH isozymes of G. mirabilis a major role in determining the metabolic fate of pyruvate, which can be channneled preferentially towards the Krebs cycle at low temperatures and efficiently converted to lactate at higher temperatures.

Abstract: 1. 1. The lactate dehydrogenase (LDH) isozymes present in white skeletal muscle of Gillichthys mirabilis exhibit substrate (pyruvate) inhibition only at temperature below 25°C. The extent of pyruvate inhibition is inversely proportional to temperature. 2. 2. The apparent K m of pyruvate is essentially temperature-independent between 10 and 25°C. At higher temperature in the organism's physiolohgical range the apparent K m of pyruvate increases as temperature is raised. 3. 3. These temperature-dependent kinetic properties may give the LDH isozymes of G. mirabilis a major role in determining the metabolic fate of pyruvate. 4. 4. At higher temperatures, when oxygen availability is reduced and the orgnism's activity level is apt to be relatively high, pyruvate may be efficiently converted to lactate, i.e. the fish can rely on anaerobic glycolysis. 5. 5. At low temperatures, when the opposite conditions of oxygen avalability and organismal activity pertain, pyruvate can be channneled preferentially towards the Krebs cycle.